TOKYO – The scientist accused of falsifying data in a widely heralded stem-cell research paper says that despite mistakes in her work the results are valid.

Haruko Obokata struggled at times to maintain her composure during a news conference Wednesday in the western city of Osaka.

She insisted she did not tamper with the data to fabricate her results, and said she does not intend to retract a report that appeared in the scientific journal Nature.

Obokata apologized repeatedly for having used the wrong images and having altered an image in a report on using a simple lab procedure to grow tissue for treating illnesses such as diabetes and Parkinson’s disease.

She has contested allegations of research malpractice made by a panel of scientists at the government-funded Riken Center for Development Biology.